Then I noticed FreeBIOS. It supersedes OpenBIOS,
and is in active development. (Note: I asked some
questions on the OpenBIOS IRC channel, and was
not directed towards FreeBIOS?). Anyway, you need
to download the cvs tree, so:

[RM adds: Pádraig also mentions elsewhere that the flash_utils
(flash_lock and flashcp) from the
mtd user space
package will take
snapshots of ROM contents. He also points out that one advantage
of his general approach of using Linux instead of DOS/Windows is
that you can upgrade BIOSes remotely. He also mentions the related
/dev/nvram device:

# mknod /dev/nvram c 10 144
# insmod nvram
Now one can read/write the 114 bytes of nvram.
(14 of the 128 are for the RTC.)
It also parses some of the info to /proc/driver/nvram.